1. Field of the Invention
The invention relates to a flat heater which is used for an application in the range of heating voltages of up to 1000V.
2. Brief Description of the Background of the Invention Including Prior Art
Present solutions are particularly concerned with electrically conductive materials of various nature being directly woven in or embroidered on ready fabrics. To this end, for example, metallic, metal coated carbon fibers or cellulose fibers are employed, as can be obtained according to DE 4426966 C2 or DE 19537726 C2. Furthermore, in the case of electrically conductive felts, carbon fibers are used according to DE 2303389 C2 and DE 2305105 A1 which are manufactured by carbonizing of, inter alia, cellulose material. Thereby the manufacture is carried out via the steps fiber manufacture, weaving, preparation and finishing the flat heater in a plurality of steps and is very expensive.
Even more recent applications such as DE 19848860 A1, DE 29808842 U and DE 19509153 A1 describe flat heaters made of nonwoven which consist of carbon fibers. In said applications cellulose nonwoven is not mentioned. Furthermore, DE 19911519 A1 discloses a glass fiber nonwoven material which contains portions of carbon fiber. The solutions specified in the mentioned publications start, however, from nonwovens which have to be formed first from filaments and fibers, respectively. The manufacturing of the nonwovens in the course of the fiber or filament production is neither disclosed nor claimed. Manufacturing of spunbonded nonwovens from carbon fibers is not possible.